Be more picky in parse_literal_maybe_minus.

By only accepting `NtExpr` if it's a literal (possibly with a unary minus). This means various error cases are caught during parsing, instead of during HIR lowering, and the `ArbitraryExpressionInPattern` error is no longer needed.
rust-lang · Jun 17, 2024 · 74a18a0 · 74a18a0
1 parent 494db01
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diff --git a/compiler/rustc_ast_lowering/messages.ftl b/compiler/rustc_ast_lowering/messages.ftl
@@ -3,10 +3,6 @@ ast_lowering_abi_specified_multiple_times =
     .label = previously specified here
     .note = these ABIs are equivalent on the current target
 
-ast_lowering_arbitrary_expression_in_pattern =
-    arbitrary expressions aren't allowed in patterns
-    .pattern_from_macro_note = the `expr` fragment specifier forces the metavariable's content to be an expression
-
 ast_lowering_argument = argument
 
 ast_lowering_assoc_ty_binding_in_dyn =

diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
@@ -363,15 +363,6 @@ pub struct NeverPatternWithGuard {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(ast_lowering_arbitrary_expression_in_pattern)]
-pub struct ArbitraryExpressionInPattern {
-    #[primary_span]
-    pub span: Span,
-    #[note(ast_lowering_pattern_from_macro_note)]
-    pub pattern_from_macro_note: bool,
-}
-
 #[derive(Diagnostic)]
 #[diag(ast_lowering_inclusive_range_with_no_end)]
 pub struct InclusiveRangeWithNoEnd {

diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
@@ -1,6 +1,4 @@
-use super::errors::{
-    ArbitraryExpressionInPattern, ExtraDoubleDot, MisplacedDoubleDot, SubTupleBinding,
-};
+use super::errors::{ExtraDoubleDot, MisplacedDoubleDot, SubTupleBinding};
 use super::ResolverAstLoweringExt;
 use super::{ImplTraitContext, LoweringContext, ParamMode};
 use crate::ImplTraitPosition;
@@ -338,14 +336,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             | ExprKind::Dummy => {}
             ExprKind::Path(..) if allow_paths => {}
             ExprKind::Unary(UnOp::Neg, inner) if matches!(inner.kind, ExprKind::Lit(_)) => {}
-            _ => {
-                let pattern_from_macro = expr.is_approximately_pattern();
-                let guar = self.dcx().emit_err(ArbitraryExpressionInPattern {
-                    span: expr.span,
-                    pattern_from_macro_note: pattern_from_macro,
-                });
-                return self.arena.alloc(self.expr_err(expr.span, guar));
-            }
+            kind => panic!("unexpected expr kind {kind:?}"),
         }
         self.lower_expr(expr)
     }

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
@@ -2197,15 +2197,26 @@ impl<'a> Parser<'a> {
     /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
     /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
     pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
-        if let token::Interpolated(nt) = &self.token.kind {
+        let whole = if let token::Interpolated(nt) = &self.token.kind {
             match &**nt {
-                token::NtExpr(e) | token::NtLiteral(e) => {
-                    let e = e.clone();
-                    self.bump();
-                    return Ok(e);
-                }
-                _ => {}
-            };
+                token::NtLiteral(e) => Some(e.clone()),
+                token::NtExpr(e) => match &e.kind {
+                    ExprKind::Lit(_) => Some(e.clone()),
+                    ExprKind::Unary(UnOp::Neg, inner)
+                        if matches!(&inner.kind, ast::ExprKind::Lit(_)) =>
+                    {
+                        Some(e.clone())
+                    }
+                    _ => None,
+                },
+                _ => None,
+            }
+        } else {
+            None
+        };
+        if let Some(e) = whole {
+            self.bump();
+            return Ok(e);
         }
 
         let lo = self.token.span;

diff --git a/tests/ui/issues/issue-43250.rs b/tests/ui/issues/issue-43250.rs
@@ -4,10 +4,10 @@ fn main() {
     macro_rules! m {
         ($a:expr) => {
             let $a = 0;
+            //~^ ERROR expected pattern, found expression `y`
+            //~| ERROR expected pattern, found expression `C`
         }
     }
     m!(y);
-    //~^ ERROR arbitrary expressions aren't allowed in patterns
     m!(C);
-    //~^ ERROR arbitrary expressions aren't allowed in patterns
 }
diff --git a/tests/ui/issues/issue-43250.stderr b/tests/ui/issues/issue-43250.stderr
@@ -1,18 +1,24 @@
-error: arbitrary expressions aren't allowed in patterns
-  --> $DIR/issue-43250.rs:9:8
+error: expected pattern, found expression `y`
+  --> $DIR/issue-43250.rs:6:17
    |
+LL |             let $a = 0;
+   |                 ^^ expected pattern
+...
 LL |     m!(y);
-   |        ^
+   |     ----- in this macro invocation
    |
-   = note: the `expr` fragment specifier forces the metavariable's content to be an expression
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: arbitrary expressions aren't allowed in patterns
-  --> $DIR/issue-43250.rs:11:8
+error: expected pattern, found expression `C`
+  --> $DIR/issue-43250.rs:6:17
    |
+LL |             let $a = 0;
+   |                 ^^ expected pattern
+...
 LL |     m!(C);
-   |        ^
+   |     ----- in this macro invocation
    |
-   = note: the `expr` fragment specifier forces the metavariable's content to be an expression
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/lowering/expr-in-pat-issue-99380.rs b/tests/ui/lowering/expr-in-pat-issue-99380.rs
@@ -1,11 +1,11 @@
 macro_rules! foo {
     ($p:expr) => {
-        if let $p = Some(42) {
+        if let $p = Some(42) { //~ ERROR expected pattern, found expression `Some(3)`
             return;
         }
     };
 }
 
 fn main() {
-    foo!(Some(3)); //~ ERROR arbitrary expressions aren't allowed in patterns
+    foo!(Some(3));
 }
diff --git a/tests/ui/lowering/expr-in-pat-issue-99380.stderr b/tests/ui/lowering/expr-in-pat-issue-99380.stderr
@@ -1,10 +1,13 @@
-error: arbitrary expressions aren't allowed in patterns
-  --> $DIR/expr-in-pat-issue-99380.rs:10:10
+error: expected pattern, found expression `Some(3)`
+  --> $DIR/expr-in-pat-issue-99380.rs:3:16
    |
+LL |         if let $p = Some(42) {
+   |                ^^ expected pattern
+...
 LL |     foo!(Some(3));
-   |          ^^^^^^^
+   |     ------------- in this macro invocation
    |
-   = note: the `expr` fragment specifier forces the metavariable's content to be an expression
+   = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/macros/trace_faulty_macros.rs b/tests/ui/macros/trace_faulty_macros.rs
@@ -43,10 +43,10 @@ fn use_bang_macro_as_attr() {}
 fn use_derive_macro_as_attr() {}
 
 macro_rules! test {
-    (let $p:pat = $e:expr) => {test!(($p,$e))};
+    (let $p:pat = $e:expr) => {test!(($p,$e))}; //~ ERROR expected pattern, found expression `1+1`
     // this should be expr
     //           vvv
-    (($p:pat, $e:pat)) => {let $p = $e;}; //~ ERROR expected expression, found pattern `1+1`
+    (($p:pat, $e:pat)) => {let $p = $e;};
 }
 
 fn foo() {

diff --git a/tests/ui/macros/trace_faulty_macros.stderr b/tests/ui/macros/trace_faulty_macros.stderr
@@ -69,22 +69,18 @@ LL | #[derive(Debug)]
 LL | fn use_derive_macro_as_attr() {}
    | -------------------------------- not a `struct`, `enum` or `union`
 
-error: expected expression, found pattern `1+1`
-  --> $DIR/trace_faulty_macros.rs:49:37
+error: expected pattern, found expression `1+1`
+  --> $DIR/trace_faulty_macros.rs:46:42
    |
 LL |     (let $p:pat = $e:expr) => {test!(($p,$e))};
-   |                                          -- this is interpreted as expression, but it is expected to be pattern
+   |                                          ^^ expected pattern
 ...
 LL |     (($p:pat, $e:pat)) => {let $p = $e;};
-   |                                     ^^ expected expression
+   |               ------ while parsing argument for this `pat` macro fragment
 ...
 LL |     test!(let x = 1+1);
-   |     ------------------
-   |     |             |
-   |     |             this is expected to be expression
-   |     in this macro invocation
+   |     ------------------ in this macro invocation
    |
-   = note: when forwarding a matched fragment to another macro-by-example, matchers in the second macro will see an opaque AST of the fragment type, not the underlying tokens
    = note: this error originates in the macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: trace_macro
@@ -107,7 +103,6 @@ LL |     test!(let x = 1+1);
    = note: expanding `test! { let x = 1+1 }`
    = note: to `test! ((x, 1+1))`
    = note: expanding `test! { (x, 1+1) }`
-   = note: to `let x = 1+1;`
 
 error: aborting due to 5 previous errors
 

diff --git a/tests/ui/macros/vec-macro-in-pattern.rs b/tests/ui/macros/vec-macro-in-pattern.rs
@@ -4,7 +4,7 @@
 
 fn main() {
     match Some(vec![42]) {
-        Some(vec![43]) => {} //~ ERROR arbitrary expressions aren't allowed in patterns
+        Some(vec![43]) => {} //~ ERROR expected pattern, found expression
         _ => {}
     }
 }
diff --git a/tests/ui/macros/vec-macro-in-pattern.stderr b/tests/ui/macros/vec-macro-in-pattern.stderr
@@ -1,11 +1,14 @@
-error: arbitrary expressions aren't allowed in patterns
+error: expected pattern, found expression `< [_] > :: into_vec(#[rustc_box] $crate :: boxed :: Box :: new([43]))`
   --> $DIR/vec-macro-in-pattern.rs:7:14
    |
 LL |         Some(vec![43]) => {}
    |              ^^^^^^^^
+   |              |
+   |              expected pattern
+   |              in this macro invocation
+   |              this macro call doesn't expand to a pattern
    |
-   = note: the `expr` fragment specifier forces the metavariable's content to be an expression
-   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `$crate::__rust_force_expr` which comes from the expansion of the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/match/expr_before_ident_pat.rs b/tests/ui/match/expr_before_ident_pat.rs
@@ -2,12 +2,11 @@ macro_rules! funny {
     ($a:expr, $b:ident) => {
         match [1, 2] {
             [$a, $b] => {}
+            //~^ ERROR expected pattern, found expression `a`
         }
     };
 }
 
 fn main() {
     funny!(a, a);
-    //~^ ERROR cannot find value `a` in this scope
-    //~| ERROR arbitrary expressions aren't allowed in patterns
 }
diff --git a/tests/ui/match/expr_before_ident_pat.stderr b/tests/ui/match/expr_before_ident_pat.stderr
@@ -1,17 +1,13 @@
-error[E0425]: cannot find value `a` in this scope
-  --> $DIR/expr_before_ident_pat.rs:10:12
+error: expected pattern, found expression `a`
+  --> $DIR/expr_before_ident_pat.rs:4:14
    |
+LL |             [$a, $b] => {}
+   |              ^^ expected pattern
+...
 LL |     funny!(a, a);
-   |            ^ not found in this scope
-
-error: arbitrary expressions aren't allowed in patterns
-  --> $DIR/expr_before_ident_pat.rs:10:12
-   |
-LL |     funny!(a, a);
-   |            ^
+   |     ------------ in this macro invocation
    |
-   = note: the `expr` fragment specifier forces the metavariable's content to be an expression
+   = note: this error originates in the macro `funny` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0425`.
diff --git a/tests/ui/parser/issues/issue-65122-mac-invoc-in-mut-patterns.rs b/tests/ui/parser/issues/issue-65122-mac-invoc-in-mut-patterns.rs
@@ -4,21 +4,20 @@
 macro_rules! mac1 {
     ($eval:expr) => {
         let mut $eval = ();
-        //~^ ERROR `mut` must be followed by a named binding
+        //~^ ERROR expected identifier, found expression `does_not_exist!()`
     };
 }
 
 macro_rules! mac2 {
     ($eval:pat) => {
         let mut $eval = ();
-        //~^ ERROR `mut` must be followed by a named binding
-        //~| ERROR expected identifier, found `does_not_exist!()`
+        //~^ ERROR expected identifier, found `does_not_exist!()`
+        //~| ERROR `mut` must be followed by a named binding
     };
 }
 
 fn foo() {
     mac1! { does_not_exist!() }
-    //~^ ERROR cannot find macro `does_not_exist` in this scope
     mac2! { does_not_exist!() }
     //~^ ERROR cannot find macro `does_not_exist` in this scope
 }

diff --git a/tests/ui/parser/issues/issue-65122-mac-invoc-in-mut-patterns.stderr b/tests/ui/parser/issues/issue-65122-mac-invoc-in-mut-patterns.stderr
@@ -1,13 +1,12 @@
-error: `mut` must be followed by a named binding
-  --> $DIR/issue-65122-mac-invoc-in-mut-patterns.rs:6:13
+error: expected identifier, found expression `does_not_exist!()`
+  --> $DIR/issue-65122-mac-invoc-in-mut-patterns.rs:6:17
    |
 LL |         let mut $eval = ();
-   |             ^^^^ help: remove the `mut` prefix
+   |                 ^^^^^ expected identifier
 ...
 LL |     mac1! { does_not_exist!() }
    |     --------------------------- in this macro invocation
    |
-   = note: `mut` may be followed by `variable` and `variable @ pattern`
    = note: this error originates in the macro `mac1` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: expected identifier, found `does_not_exist!()`
@@ -34,16 +33,10 @@ LL |     mac2! { does_not_exist!() }
    = note: this error originates in the macro `mac2` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: cannot find macro `does_not_exist` in this scope
-  --> $DIR/issue-65122-mac-invoc-in-mut-patterns.rs:22:13
+  --> $DIR/issue-65122-mac-invoc-in-mut-patterns.rs:21:13
    |
 LL |     mac2! { does_not_exist!() }
    |             ^^^^^^^^^^^^^^
 
-error: cannot find macro `does_not_exist` in this scope
-  --> $DIR/issue-65122-mac-invoc-in-mut-patterns.rs:20:13
-   |
-LL |     mac1! { does_not_exist!() }
-   |             ^^^^^^^^^^^^^^
-
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/tests/ui/pattern/issue-92074-macro-ice.rs b/tests/ui/pattern/issue-92074-macro-ice.rs
@@ -7,21 +7,19 @@ fn get_usize() -> usize {
 }
 
 macro_rules! force_expr {
-    ($e:expr) => { $e }
+    ($e:expr) => { $e } //~ ERROR expected pattern, found expression `Vec :: new()`
 }
 
 macro_rules! force_pat {
-    ($a:expr, $b:expr) => { $a..=$b }
+    ($a:expr, $b:expr) => { $a..=$b } //~ ERROR expected pattern, found expression `get_usize()`
 }
 
 macro_rules! make_vec {
-    () => { force_expr!(Vec::new()) } //~ ERROR arbitrary expressions aren't allowed
+    () => { force_expr!(Vec::new()) }
 }
 
 macro_rules! make_pat {
     () => { force_pat!(get_usize(), get_usize()) }
-    //~^ ERROR arbitrary expressions aren't allowed
-    //~| ERROR arbitrary expressions aren't allowed
 }
 
 #[allow(unreachable_code)]